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Calculation example
9
Load bearing length, L, for tension
or compression piles
Fw
Safe working load
S
Safety factor
p
3.142
D
Grout body diameter
q sk
Ultimate skin friction
E
xample:
Required load:
22.5 kips
Material:
sand
Drill bit diameter, d:
4.4”
Ultimate skin friction q sk
21 psi
1) Grout body diameter, D:
D = d · (enlargement factor for sand)
The enlargement factor for sand is 1.5
(please see page 3).
2) Load bearing length, L:
Load bearing capacity, F CP ,
of compression only piles
Compression only piles have the ability
to spread the load over the steel sec-
tion and the grout body as a composite
pile.
Example:
CTS/TITAN BAR
TM
52/26
Outer bar diameter
2”
Ultimate strength of bar,
F U
209 kips
Drill bit diameter,
d
6.9”
Enlargement factor for ground
(conservative estimate)
1
Grout compressive strength
G C
after 28 days
5.8 ksi
Load taken on grout
(conservative
estimate)
F G
Load taken on grout
A G
Grout area
G C
Grout compressive strength
The area of the grout is calculated as
the area of the grout body minus the
steel area. (In the example, the grout
body diameter is assumed to be the
same as the drill bit diameter):
Consequently, the load taken by the
grout is
The Design Load taken on steel, F S
becomes, with the ultimate strength F U
of the CTS/TITAN BAR
TM
52/26,
The total working load
,
F CP
, of the
pile in this conservative estimate is
F CP = F G + F S
»
50 + 125 kips or
F CP
»
175 kips
Please Note
: These examples are
applicable to CTS/TITAN IBO ® micro
piles only. Design requirements and
safety factors may vary.
1 mm = 0.03937 in 1 m = 3.281 ft 1 MPa = 0.145 ksi 1kN/m 2 = 0.02088 kips/sqft